The automatic generation of formal specificationsfrom requirements suppresses the complexity of formalmodels manual creation and reveals the immediate benefitsof its usage, such as the possibility to carry out refinements,and property verification, which contributes toproject cost reduction and quality improvement. This paperproposes a Controlled Natural Language (CNL), asubset of English, used to write use case specificationsaccording to a template. From these use cases a completestrategy and tools enable the generation of processalgebraic formal models in the CSP notation. We definetemplates that represent requirements at different levelsof abstraction, capturing different views of the system behavior.Moreover, a refinement notion is defined to connectthe generated CSP models through an event mappingrelation between abstract and concrete models. This notionis further applied to detail use case specifications andto automate its execution.